Dutch club FC Twente is still unsure of the severity of Oguchi Onyewu's back injury after the hulking American defender was forced to leave a Dutch Cup match on Wednesday versus PSV Eindhoven in the first half.

It was just Onyewu's third match with the reigning Eredivisie champions since being acquired on-loan from Italian Serie A club AC Milan.

The former Standard Liege man had played the full 90 minutes in his first two contests with Twente before the unfortunate tweak in his back occured.

Twente did specify that it is a muscular problem, however they currently are not certain of how serious Onyweu's condition may be and that they hope to know more by the end of the weekend.

"At this moment, it's hard to say how serious the injury is," said Twente Press Director Richard Peters to YA. "It is something with a muscle in his back. We will know more in the coming days."

Twente defeated their league rivals in the cup match 1-1 (7-6) in a penalty shootout. They return to Eredivisie action on Sunday versus Feyenoord.